A program that interpret (and sometimes compile and run, writing executable into random memory segmant and execute in place) random file fetched from random net

A program that interpret (and sometimes compile and run, writing executable into random memory segmant and execute in place) random file fetched from random network location. You would definitely say it is a malware if you didn't know you are looking at a browser. The behavior of browser and malware really isn't that much different. I guess there really isn't a good way to know a browser binary is safe without manual intervention.